BERLIN (Reuters) - Germany's chief of defence has warned that the West must not underestimate Moscow's military strength, saying Russia has the scope to open up a second front should it choose to do so."The bulk of the Russian land forces may be tied down in Ukraine at the moment but, even so, we should not underestimate the Russian land forces' potential to open a second theatre of war," General Eberhard Zorn, the highest-ranking soldier of the Bundeswehr, told Reuters in an interview.Beyond the army, Russia also has a navy and air force at its disposal, he added."Most of the...